Unformatted text preview:

Lecture 4:�Biomaterials Surfaces: Chemistry�Hydrolysis�Supporting notes�3.051J/20.340J Materials for Biomedical Applications, Spring 2006 1Hydrolysis�• Hydrolysis is a kind of “Solvolysis”, solvent +lysis: cleavage by the solvent. BrH2O 3OHOCH3OCOHl CH OH HCOOH 2-Bromo-2-methy propane + HBr Hydoloysis + HBr Methanolysis + HBr Formic acidolysis 2Polymer Hydrolysis�•�Polymers prepared by polycondensation can be susceptible to hydrolysis. n 1,4-Butanediol + HOOHOOn OOHHSuccinic acid OO**OOn 2O l Δ H+ -, + nHAs, Zn cata ysts, , OH or enzyme Poly(butylene succinate), PBS 3Hydrolysable is “degradable”.�Synthetic polymers�· Polyesters · Polyamides · Polyanhydrides · Polyethers · Polyurethanes · Polycarbonates · Polyureas Material properties can be tuned readily. Cheaper! Naturally-occurring polymers · Proteins and polyamides Collagen Fibrinogen and fibrin Gelatin Casein · Polysaccharides Cellulose Starch and amylose Chitin and chitosan Dextran · Polynucleotides DNA and RNA 4Biodegradation:�An event which takes place through the action of enzymes and/or chemical decomposition associated with living organisms (bacteria, fungi, etc.) or their secretion products. AlbertssonandKarlsson, in Chemistry and Technology of Biodegradable Polymers 1994 O R CON R COHO R O COPolyester Polyamide Polycarbonate C R O COON PRR'OOOOR"R'ROPolyanhydride Polyphosphazene Poly(ortho ester) Typical examples of synthetic biodegradable polymers 5Key factors in hydrolysis�1. Bond stability Example: Hydrolysis of polyester C Oδ+ δ-Base-catalyzed polyester hydrolysis δ-δ+ OCR O R'-OC-R O R'OHO-CR O R'OHH+ OCR OH+ R’OHOH 6Acid-catalyzed polyester hydrolysis δ-H+ δ+ OCR O R'O+CR O R'HOC+R O R'HOCR O+R'HHOHOCR O R'HO+HH-H+H2O + R’OH OCR OHPolyamide hydrolysis H2O OCR N R'HOCR OH+ H2N-R’ 7Key factors in hydrolysis�2. Hydrophobicity 3. Molecular weight & architecture4. Morphology Crystallinity, porosity 5. Tg Mobility of polymer chain Chance to contact with H2O 80 80 90 � a (degrees)100 120 12 24 36 48 0 12 24 36 48 Amorphous PLLA Crystalline PLLA 108 110 Alkaline Treatment Time (h) Alkaline Treatment Time (h) 113Orthorhombic crystal structure of α-PLLA�Figures removed for copyright reasons. 6.1 28.8 ddcrystal: 1.290 g/cm3 amorphous: 1.248 g/cm3 10.5 Å 10Hydrolysable polymers�Polyanhydride OCR O C R'OOCR O R'OCR N R'HH2O OCR OHOCR OHOCR OH+ Polyester H2O + Polyamide H2O + Polyether OR R'OHRH2O + Polyether urethane OCO N R'HRR NHCON R'HR O COO R'H2O OHR+ OCHO R'HO R'H2N R'HO R'OCHO N R'HPolyurea H2O R NHCOOHR O COOH+ H2N R'Polycarbonate H2O + HO R'11Poly(sebacic anhydride)�Properties: rapid degradation, Tg: 50 °C, Tm : 80 °C Uses: drug delivery matrices OO OTable. Half-lives of hydrolyzable polymers Incorporation ofPolymer class Half-life hydrophobic segment Polyanhydrides 0.1 h PLLA 3.3 years 83,000 years Poly(bis-(p-carboxyphenoxy)propane-co-sebacic anhydride)COO C3H6O OO OC8H16OOPolyamides Tabata et al., Pharm. Res., 10, 391, 1993 Göpferich,Biomater., 17, 103, 1996 12Poly(glycolide-co-lactide) (polyglactide) Properties: rapid degradation, amorphous*, Tg: 45-55 °C Uses: bioresorbable sutures, controlled release matrices, tissue engineering scaffolds *Depending on composition OOOOGlycolate Lactate (GA) (DL-LA) Dexon®: the first synthetic bioresorbable suture in 1960s. (PGA)�Histological response can be predictable in comparison to non-synthetic materials. High-crystalline nature limits processability. 13Poly(L-lactide), poly(L-lactic acid) (PLLA) Properties: rapid degradation, semicrystalline, Tg: 60 °C, Tm: 180 °C Uses: fracture fixation, ligament augmentation OO*PLLA OHHOHHOHOHOHHHOHHOOOH*OO*Fermentation -H2O microorganisms e.g. LactobacilliL-lactic acid OO OO**PLLAD-glucose from agricultural product; -H2Ocorn, potato, rice L-lactide 14Physical properties of various plastics�PLLA PET PS PP�Density/g/cm3 1.27 1.34 1.04 0.90 Tensile strength/MPa 66.7 55.9 43.1 37.3 Yong’s modulus/MPa 3300 2600 3300 2100 Elongation@break/% 4 300 2 700 Cost/$/lb 1-5 0.75 0.55 -*Polymeric materials were non-oriented (as prepared). Tsuji, Polylacticacid, JPS press, Kyoto, 1997, Ikada,Macromol. RapidCommun., 21, 117, 2000 15OPolyethylene oxide (PEO) Properties: water soluble, semicrystalline, Tg: -60 °C, Tm: 60 °C Uses: hydrogel, protein-resistant coatings Two photos removed for copyright reasons. PEO Figure 6 in Irvine, D., et al. "Nanoscale Clustering of RGD Peptides at Surfaces Using Comb Polymers. 1. Synthesis and Characterization of Comb Thin Films." Biomacromolecules 2, no. 1 (2001): 85 -94. Rate of hydrolysis: anhydride > ester >> amide >>>> ether etc. Matrices for drug delivery 16Hydrolysis of polymeric materials�Acid- or base-catalyzed hydrolysis Time MW Enzymatic hydrolysis -surface erosion-Time MW 17Hydrolysis of Bionole® (PBS)�OO**OOPhotos removed for copyright reasons. Alkaline treated Lipase PS treatedTaniguchi I., unp ub lished results 18Application of biodegradable polymers and minimal requirements of biomaterials PAA: PBS: PCA: PCL: PEA: PGA: PGALA: PDLLA: PDLLA PGALA PGA PCA POE PAA Starch PLLA PHA (PHB) PCL PEC PBS PES PEA Chitin PPZ Fibrin Application of Biodegradable Polymers Poly(acid anhydride) Poly(butylene succinate) Poly(�-cyanoacrylate) Poly(�-caprolactone) Poly(ester amide) Poly(glycolide), Poly(glycolic acid) Poly(glycolide-co-lactide), Poly(glycolic acid-co-lactic acid) Poly(DL-lactide), Poly(DL-lactic acid) PHA: PHB: PLLA: POE: PEC: PES: Poly(hydroxyalkanoate Poly(3-hydroxybutyrate) Poly(L-lactide), Poly(L-lactic acid) Poly(orthoester) Poly(ester carbonate) Poly(ethylene succinate) Oxidized cellulose CelluloseHyaluronate Collagen Medical Application Ecological Application Minimal Requirements of Biomaterials B) Effective Functionality, Performance, Durability, etc. C) Sterilizable Ethylene oxide, Θ-Irradiation, Electron beams, Autoclave, Dry heating, etc. D) Biocompatible Interfacially, Mechanically, and Biologically A) Non-toxic (biosafe) Non-pyrogenic, Non-hemolytic, Chronically non-inflammative, Non-allergenic, Non-carcinogenic, Non-teratogenic, etc. Figure by MIT OCW. 19 Figure by MIT OCW.ControlWithS.waywayandensisJCM 9114WithA.orientalis subsp. OrientalisIFO 12362Microbial degradation of PLLA (rare case)�Photos removed for copyright reasons. OO*Hydrolysable polymer Esterases do not degrade except proteinase K. PLLA�Figure. SEM images of PLLA film treated with microbe Jarerat et al.,


View Full Document
Download Lecture 4 Biomaterials Surfaces:Chemistry
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Lecture 4 Biomaterials Surfaces:Chemistry and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Lecture 4 Biomaterials Surfaces:Chemistry 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?